Alpha-herpesviruses are neurotropic pathogens that include the human viruses varicella-zoster virus (VZV) and herpes simplex virus (HSV) types 1 and 2, and the animal virus pseudorabies virus (PRV). These viruses spread into the nervous system by directed axonal transport to sensory neuron cell bodies in peripheral ganglia, where life-long latent infections are established. Infections are typically not life threatening in healthy individuals, however, these viruses have the capacity to spread trans-synaptically to enter the brain by circuit-specific routes. Once in the brain, the resulting encephalitis is lethal in the majority of cases. The long-term goals of my studies are to determine the mechanisms by which alpha-herpesviruses spread in the nervous system, and to identify the factors governing disease outcome. This application will focus on virus spread in the axons of sensory neurons. Specifically: Using infectious clone mutagenesis methods, viruses will be isolated carrying mutations in the genes encoding each tegument protein. The mutant viruses will be screened for defects in capsid transport in axons by time-lapse tracking of capsids fused to the green-fluorescence protein. Structure/function analysis of tegument proteins required for capsid transport will be initiated. In this way, the role of the viral tegument proteins in capsid transport will be definitively tested. These proteins are expected to both tether capsids to microtubule motors and regulate motor activity, as no other class of viral proteins are known to associate with capsids and be exposed to the host cytosol simultaneously. The results of these studies will determine how alpha-herpesviruses move directionally within sensory neurons. This will serve as a first step to identifying the molecular mechanisms of viral transport, and to addressing the larger question of virus spread in the vertebrate nervous system.